Received: from zonker-fddi.hpl.hp.com by opus.hpl.hp.com with SMTP (1.37.109.8/15.5+ECS 3.3+HPL1.1) id AA20169; Tue, 13 Dec 1994 17:42:22 -0800 Return-Path: <poulton@zonker.hpl.hp.com-DeleteThis> Received: by zonker.hpl.hp.com (1.37.109.8/15.5+ECS 3.3+HPL1.1) id AA28444; Tue, 13 Dec 1994 17:42:15 -0800 Date: Tue, 13 Dec 1994 17:42:15 -0800 From: Ken Poulton <poulton@zonker.hpl.hp.com-DeleteThis> Message-Id: <9412140142.AA28444@zonker.hpl.hp.com-DeleteThis> To: wind_talk@opus.hpl.hp.com-DeleteThis Subject: Re: Tide Data
> Just curious whether anyone actually uses tide data for anything?
Every sailing day! I have built a list of safe tide levels for the
peninsula sailing sites and I check an hourly tide graph to decide what
hours are safe at a particular site. At 3rd, I pay attention to both
the tide level (for sand bars) and to when the ebb is runing (for the
swell).
> I have to obtain the data tide data from a different source than the current
> data.
I have a program that calculates tides at various Bay sites, but it needs
a bit of work before I release it. Maybe over Christmas.
> On a related note, does anyone know why high/low tide times differ
> (sometimes substantially) from slack times? I noticed this in my tide
> book and it didn't make much sense to me. Could it be that there's a lag
> between when slack occurs and the tide actually hits its highest (or lowest)
> point (e.g. during a full moon)?
EE's will have no problem with this - the Bay is just a distributed RC
transmission line. In simpler terms, it takes a while for the tidal
change at the ocean to propagate up the Bay - this is why there are
delays from the Gate to other sites (like around 5 hours to Rio). The
tranmission is not perfect, however, and the result is that
when the tide is high at the Gate, current is still running into the
Gate to fill other parts of the Bay. Slack water doesn't happen
until around 2 hours later when the Gate tide level is coming back down.
Ken Poulton
poulton@opus.hpl.hp.com-DeleteThis
"Alice laughed. `There's no use trying,' she said: `one *can't*
believe impossible things.'
'I dare say you haven't had much practice,' said the Queen.
`When I was your age, I always did it for half-an-hour a day.
Why, sometimes I've believed as many as six impossible things
before breakfast.'" -- The White Queen to Alice
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